Hybridomas are being produced which secrete monoclonal antibodies of defined antigen specificity and antibody subclass. Studies have demonstrated means for improving the yield of hybridomas. Using these methods a number of hybridomas have been produced including anti-DNP IgE, anti Actinomyces viscosus, anti-Cytophaga sp, anti-lymphokines (IL 1 and IL 2), anti-Fc receptor of mast cells, anti-human IgE, and anti-idiotype. These monoclonal antibodies are being utilized in a number of biochemical and biological studies.